Armature and motor

ABSTRACT

In an armature, a plurality of teeth extending from an annular core back each include a projection portion arranged to extend in a circumferential direction from a circumferential side surface of the tooth. Insulators, each of which is attached to the stator core and is arranged to cover at least a portion of a separate one of the teeth, include an insulator contact surface arranged to be in contact with the projection portion. A portion of the projection portion and the insulator contact surface are arranged to be in contact with each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an armature and a motor.

2. Description of the Related Art

An umbrella-less core is sometimes used as a stator core of an armatureto design a magnetic circuit. The umbrellaless core refers to a corehaving an umbrellaless structure, in which stator teeth have no umbrellaportions.

A stator described in JP-A 2008-312288 includes a stator core includingstator teeth, insulating members, each of which includes an opening tobe fitted to a separate one of the stator teeth, and stator coils, eachof which is wound around a separate one of the insulating members. Theopenings are fitted to the respective stator teeth in a situation inwhich the stator core has been cooled. According to a method of fixingan insulator to the stator core disclosed in JP-A 2008-312288, eachinsulating member is fitted to a corresponding one of the stator teethin a situation in which the stator teeth have shrunk as a result ofcooling of the stator core, and when the stator teeth thereafter returnto their original volume at ordinary temperatures, a gap between eachinsulating member and the corresponding stator tooth is reduced.

In the case of the method disclosed in JP-A 2008-312288, however, strictcontrol of precision in dimensions of each component is required to fixthe insulator to the stator core.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide an armature whichincludes a stator core including an umbrella-less structure and whichallows secure fixing of insulators.

An armature according to a preferred embodiment of the present inventionincludes a stator core including an annular core back and a plurality ofteeth, insulators, and coils. The teeth are arranged to extend radiallyinward or radially outward from the annular core back. Each insulator isattached to the stator core and is arranged to cover at least a separateone of the teeth. Each coil is defined by a conducting wire wound arounda separate one of the insulators. Each insulator includes a first resinmember and a second resin member arranged in an axial direction or acircumferential direction. Each tooth includes a projection portionarranged to extend in the circumferential direction from acircumferential side surface of the tooth. The projection portionincludes a projection portion contact surface arranged to face the coreback. Each insulator includes an insulator contact surface arranged toface a tip of a corresponding one of the teeth. The insulator contactsurface is arranged to be at least partly in contact with the projectionportion contact surface of the projection portion of the correspondingtooth.

Preferred embodiments of the present invention are able to provide anarmature which includes an umbrellaless core and which allows securefixing of insulators.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a portion of an armature accordingto a first preferred embodiment of the present invention taken along aplane perpendicular or substantially perpendicular to an axialdirection.

FIG. 2 is a cross-sectional view of a portion of the armature accordingto the first preferred embodiment taken along a plane perpendicular orsubstantially perpendicular to a direction of extension of a tooth.

FIG. 3 is a cross-sectional view of the armature according to the firstpreferred embodiment taken along a plane perpendicular or substantiallyperpendicular to the axial direction.

FIG. 4 is a cross-sectional view of a motor according to a secondpreferred embodiment of the present invention.

FIG. 5 is a cross-sectional view of a portion of an armature accordingto a modification of the first preferred embodiment of the presentinvention taken along a plane perpendicular or substantiallyperpendicular to the axial direction.

FIG. 6 is a cross-sectional view of a portion of an armature accordingto a modification of the first preferred embodiment of the presentinvention taken along a plane perpendicular or substantiallyperpendicular to a direction of extension of a tooth.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. It is assumedherein that a direction parallel or substantially parallel to a centralaxis of a motor is referred to by the term “axial direction”, “axial”,or “axially”, that directions perpendicular or substantiallyperpendicular to the central axis of the motor are referred to by theterm “radial direction”, “radial”, or “radially”, and that a directionalong a circular arc centered on the central axis of the motor isreferred to by the term “circumferential direction”, “circumferential”,or “circumferentially”. It is also assumed herein that an axialdirection is a vertical direction, and the shape of each member orportion and relative positions of different members or portions will bedescribed based on this assumption. It should be noted, however, thatthe above definitions of the various directions are made simply for thesake of convenience in description, and should not be construed torestrict in any way the orientation of an armature or a motor accordingto any preferred embodiment of the present invention when in use.

First Preferred Embodiment

FIG. 1 is a cross-sectional view of a portion of an armature 21according to a preferred embodiment of the present invention taken alonga plane perpendicular or substantially perpendicular to the axialdirection. Referring to FIG. 1, the armature 21 preferably includes astator core 4, insulators 5, and coils 6.

The stator core 4 is preferably defined by, for example, a plurality ofelectromagnetic steel sheets placed one upon another in the axialdirection. Each of the electromagnetic steel sheets is a magnetic body.The stator core 4 preferably includes a core back 41 arranged in anannular or substantially annular shape and a plurality of teeth 42arranged to extend radially inward from the core back 41. Note that theteeth 42 may be arranged to extend radially outward from the core back41.

An upper surface, a lower surface, and circumferential side surfaces ofeach of the teeth 42 are covered with a separate one of the insulators5. Each coil 6 is preferably defined by a conducting wire wound around aseparate one of the insulators 5.

Each tooth 42 preferably includes a tooth tip surface 422 and projectionportions 421 each of which is arranged to extend in a circumferentialdirection from a separate one of the circumferential side surfaces ofthe tooth 42. Each projection portion 421 is preferably arranged at atip portion of the tooth 42, and moreover, a base portion of theprojection portion 421 is preferably arranged to be continuous with thetooth tip surface 422. This arrangement contributes to minimizing areduction in space factor.

Each projection portion 421 preferably includes a tip portion 4212 and a“projection portion contact surface” 4211 arranged to face the core back41. It is desirable that both the radial thickness and thecircumferential width of the projection portion 421 should be minimizedto increase the space factor of the coil 6.

FIG. 2 is a cross-sectional view of a portion of the armature 21according to the present preferred embodiment taken along a planeperpendicular or substantially perpendicular to a direction of extensionof the tooth 42. Here, the plane perpendicular or substantiallyperpendicular to the direction of the extension of the tooth 42corresponds to a plane indicated by line A-A′ in FIG. 1.

Referring to FIG. 2, each insulator 5 preferably includes a first resinmember 51 arranged to cover an axially upper side of the tooth 42, and asecond resin member 52 arranged to cover an axially lower side of thetooth 42. Referring to FIG. 1, the insulator 5 preferably furtherincludes insulator contact surfaces 53 each of which is arranged to facea tip of the tooth 42, accommodating portions 54, insulator tip surfaces55, and “accommodating portion inner wall surfaces” 56.

The first resin member 51 preferably includes a top plate portion 511and a pair of upper side wall portions 512. The upper surface of thetooth 42 is covered with the top plate portion 511. The upper side wallportions 512 are arranged to extend downward from both circumferentialend portions of the top plate portion 511. Upper regions of bothcircumferential side surfaces of the tooth 42 are covered with the upperside wall portions 512.

The second resin member 52 preferably includes a bottom plate portion521 and a pair of lower side wall portions 522. The lower surface of thetooth 42 is covered with the bottom plate portion 521. The lower sidewall portions 522 are arranged to extend upward from bothcircumferential end portions of the bottom plate portion 521. Lowerregions of both circumferential side surfaces of the tooth 42 arecovered with the lower side wall portions 522. The above structureenables easy attachment of the insulator 5 to the tooth 42.

The insulators 5 are arranged to intervene between the teeth 42 and thecoils 6 to more effectively ensure electrical isolation between theteeth 42 and the coils 6.

Each insulator contact surface 53 is preferably defined by a portion ofone of the upper side wall portions 512 of the first resin member 51 anda portion of one of the lower side wall portions 522 of the second resinmember 52. The insulator contact surface 53 is a surface which extendscircumferentially outward in the upper side wall portion 512 of thefirst resin member 51 and the lower side wall portion 522 of the secondresin member 52. In addition, the insulator contact surface 53 isarranged to be at least partly in contact with the projection portioncontact surface 4211. This arrangement prevents the insulator 5 frommoving toward the tip of the tooth 42 to come off.

The insulator contact surface 53 is preferably arranged at end portionsof the upper side wall portion 512 of the first resin member 51 and thelower side wall portion 522 of the second resin member 52 near the tipof the tooth 42. Note, however, that this is not essential to preferredembodiments of the present invention.

Moreover, the insulator contact surface 53 is preferably arrangedthroughout the upper side wall portion 512 of the first resin member 51and the lower side wall portion 522 of the second resin member 52. Note,however, that this is not essential to preferred embodiments of thepresent invention.

Each accommodating portion inner wall surface 56 is arranged to extendfrom a circumferential end portion of a corresponding one of theinsulator contact surfaces 53 toward the tip of the tooth 42.

Each accommodating portion 54 is a portion of the insulator 5, and is ashoulder portion arranged circumferentially outside the upper side wallportion 512 and the lower side wall portion 522. The accommodatingportion 54 is arranged to cover the tip portion 4212 of a correspondingone of the projection portions 421 from circumferentially outside. Theaccommodating portion 54 includes the insulator contact surface and theaccommodating portion inner wall surface 56. This structure contributesto more securely fixing the insulator 5 to the tooth 42.

Furthermore, the accommodating portion 54 may be arranged to cover atleast a portion of an axial end surface of the tip portion 4212.

Furthermore, each projection portion 421 preferably has a thickness anda width both greater than the thickness of each electromagnetic steelsheet. This facilitates manufacturing of the projection portion 421.

Each insulator tip surface 55 is preferably a surface which extendscircumferentially outward from a radial end portion of the insulator 5.The insulator tip surface 55 is preferably has a width d1 greater than adistance d2 from a base to a tip of each projection portion 421 of thetooth 42. This structure contributes to reducing the likelihood of acollapse of the coil 6.

Note, however, that the width d1 of the insulator tip surface 55 may besmaller than the distance d2 from the base to the tip of the projectionportion 421 of the tooth 42.

The thickness t1 of a tip portion of the insulator 5 measured in adirection of extension of the tooth 42 is preferably arranged to begreater than the thickness t2 of the projection portion 421 measured ina direction parallel to the direction of the extension of the tooth 42at an exact midpoint h along the projection of the projection portion421. This contributes to preventing a pressure on the insulator 5 fromcausing a significant deformation of the insulator 5.

FIG. 3 is a cross-sectional view of the armature 21 of FIG. 1 preferablyhaving an annular or substantially annular shape. Referring to FIG. 3,an envelope S1 is defined by the tooth tip surfaces 422 and theinsulator tip surfaces 55. The envelope S1 preferably is cylindrical orsubstantially cylindrical in shape. This contributes to reducingdisturbance of air currents between surfaces of a rotor and the toothtip surfaces 422.

Second Preferred Embodiment

FIG. 4 is a cross-sectional view of a motor 1 according to anotherpreferred embodiment of the present invention. Referring to FIG. 4, themotor 1 preferably includes a stationary portion 2 and a rotatingportion 3.

The stationary portion 2 preferably includes the armature 21, a coverportion 22, a housing 23, a lower bearing portion 24, and an upperbearing portion 25.

The armature 21 includes the stator core 4, the insulators 5, and thecoils 6. The stator core 4 is preferably defined by, for example, aplurality of electromagnetic steel sheets placed one upon another in theaxial direction. Each electromagnetic steel sheet is a magnetic body.The stator core 4 preferably includes the annular core back 41 and theplurality of teeth 42. A central axis of the core back 41 coincides witha central axis J1. The teeth 42 are arranged at regular intervals in thecircumferential direction.

The lower bearing portion 24 is arranged between the housing 23 and ashaft 31 of the rotating portion 3. The upper bearing portion 25 isarranged between the cover portion 22 and the shaft 31. A ball bearingwhich causes an outer race and an inner race to rotate relative to eachother through balls is preferably used as each of the lower and upperbearing portions 24 and 25 according to the present preferredembodiment. Note, however, that other types of bearings, such as, forexample, plain bearings, fluid bearings, or the like, may be used inplace of the ball bearings.

The rotating portion 3 includes the shaft 31, a rotor core 32, and aplurality of magnets 33.

The shaft 31 is a columnar metallic member arranged to extend in thevertical direction. A central axis of the shaft 31 coincides with thecentral axis J1. The shaft 31 is arranged to rotate while beingsupported by both the lower and upper bearing portions 24 and 25described above.

The rotor core 32 and the magnets 33 are arranged radially inside thearmature 21, and are arranged to rotate together with the shaft 31. Therotor core 32 preferably is a cylindrical or substantially cylindricalmember fixed to the shaft 31.

The magnets 33 are preferably fixed to the rotor core 32 through, forexample, an adhesive such that each magnet 33 is arranged radiallyinward of an outer circumferential surface of the rotor core 32. Notethat a cover or the like may be arranged on an axial end surface of eachof the magnets 33. The magnets are preferably arranged at regular orsubstantially regular intervals in the circumferential direction suchthat north and south pole surfaces alternate with each other.

The armature 21 and the magnets 33 are preferably supported such thatthe magnets 33 are rotatable about the central axis J1 relative to thearmature 21. Once drive currents are supplied to the coils 6 of thearmature 21, magnetic flux is generated around each of the teeth 42, anda circumferential torque is produced by interaction between the magneticflux of the teeth 42 and that of the magnets 33, so that the rotatingportion 3 is caused to rotate about the central axis J1 with respect tothe stationary portion 2.

While the motor 1 according to the present preferred embodiment of thepresent invention is preferably an inner-rotor motor, other preferredembodiments of the present invention are also applicable to anouter-rotor motor in which teeth are arranged to extend radially outwardand a rotor magnet(s) is arranged radially outside the teeth.

While some preferred embodiments of the present invention have beendescribed above, it will be understood that the present invention is notlimited to the above-described preferred embodiments.

FIG. 5 is a cross-sectional view of a portion of an armature accordingto another preferred embodiment of the present invention taken along aplane perpendicular or substantially perpendicular to the axialdirection. In the preferred embodiment illustrated in FIG. 5, each ofprojection portions 421 of each of teeth 42 is arranged between a baseportion and a tip portion of the tooth 42. This structure contributes tosecurely fixing an insulator 5 to the tooth 42, and makes it possible toarbitrarily set the circumferential width of the tip portion of thetooth 42 to meet a need of magnetic circuit design.

The insulator 5 preferably includes accommodating portions 54 each ofwhich is in the shape of a groove and is arranged to cover one of theprojection portions 421. Each accommodating portion 54 preferablyincludes an insulator contact surface 53 and an accommodating portioninner wall surface 56. The insulator contact surface 53 is preferablyarranged on a side of the projection portion 421 closer to a core back41. In addition, the insulator contact surface 53 is arranged to be atleast partly in contact with the projection portion 421.

Referring to FIG. 5, the radial thickness t1 of a tip portion of theinsulator 5 is preferably arranged to be greater than the thickness t2of the projection portion 421 measured in a direction parallel orsubstantially parallel to a direction of extension of the tooth 42 at anexact midpoint h along the projection of the projection portion 421.This contributes to preventing a pressure from a coil 6 on the insulator5 from causing a significant deformation of the insulator 5.

FIG. 6 is a cross-sectional view of a portion of an armature accordingto yet another preferred embodiment of the present invention taken alonga plane perpendicular or substantially perpendicular to a direction ofextension of a tooth 42. An insulator 5 according to the preferredembodiment of the present invention illustrated in FIG. 6 preferablyincludes a first resin member 51 arranged to cover one circumferentialside of the tooth 42, and a second resin member arranged to cover anopposite circumferential side of the tooth 42.

The first resin member 51 preferably includes a first side wall portion513 and a pair of first axial wall portions 514. One circumferentialside surface of the tooth 42 is covered with the first side wall portion513. The first axial wall portions 514 are arranged to extend in thecircumferential direction from both axial end portions of the first sidewall portion 513. Portions of both axial end surfaces of the tooth 42are covered with the first axial wall portions 514.

The second resin member 52 preferably includes a second side wallportion 523 and a pair of second axial wall portions 524. An oppositecircumferential side surface of the tooth 42 is covered with the secondside wall portion 523. The second axial wall portions 524 are arrangedto extend in the circumferential direction from both axial end portionsof the second side wall portion 523. Portions of both axial end surfacesof the tooth 42 are covered with the second axial wall portions 524.This structure enables easy attachment of the insulator 5 to the tooth42.

The preferred embodiments of the present invention and modificationsthereof are applicable to motors and electric generators.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. (canceled)
 2. An armature comprising: a stator core including: anannular core back; and a plurality of teeth arranged to extend radiallyinward or radially outward from the annular core back; insulators, eachof which is attached to the stator core and is arranged to cover atleast a separate one of the teeth; and coils, each of which is definedby a conducting wire wound around a separate one of the insulators;wherein each insulator includes a first resin member and a second resinmember arranged in an axial direction or a circumferential direction;each tooth includes a projection portion arranged to extend in thecircumferential direction from a circumferential side surface of thetooth; the projection portion includes a projection portion contactsurface arranged to face the core back; each insulator includes aninsulator contact surface arranged to face a tip of a corresponding oneof the teeth; and the insulator contact surface is arranged to be atleast partly in contact with the projection portion contact surface ofthe projection portion of the corresponding tooth.
 3. The armatureaccording to claim 2, wherein the projection portion is arranged at atip portion of the tooth.
 4. The armature according to claim 3, whereinthe stator core is defined by steel sheets placed one upon another inthe axial direction; and the projection portion has a thickness and awidth which are both greater than a thickness of each steel sheet. 5.The armature according to claim 2, wherein a radial end portion of theinsulator has a radial thickness greater than a thickness of theprojection portion measured in a direction parallel or substantiallyparallel to a direction of extension of the tooth at an exact midpointalong a projection of the projection portion.
 6. The armature accordingto claim 2, wherein the insulator further includes an accommodatingportion inner wall surface arranged to extend from a circumferential endportion of the insulator contact surface toward a tip of the tooth. 7.The armature according to claim 6, wherein the insulator is arranged tocover a tip portion of the projection portion.
 8. The armature accordingto claim 2, wherein the insulator is arranged to cover an axial endsurface of the projection portion.
 9. The armature according to claim 2,wherein an envelope defined by tip surfaces of the insulators and tipsurfaces of the teeth is cylindrical or substantially cylindrical inshape.
 10. The armature according to claim 2, wherein a tip surface ofthe insulator has a width greater than a distance from a base to a tipof the projection portion.